Thank you for all the good feedback and ideas. Don't worry, I'm being very conservative. I've been through injuries before (including surgery on this same shoulder), and fully grasp the value of healing. I've been out a month already, and have been watching classes. I hadn't thought of "shadowing" the motions... I'll ask about that.
Thanks for the squats idea. I've been doing something along similar lines - when I go out to feed the horse and donkeys I do 2 sets of 20 steps up onto a straw bale and back down. That's made a huge difference in the strength in my legs, and is easy to fit into a daily routine, as I'm right there anyway twice a day. After that I do leg stretches on the pipe coral (think ballet barre!). That's helped tremendously with my right knee, which didn't want to bend as far as the left, but now is doing much better.
Don't worry about me drowning in information. I know exactly what you're talking about, but I'm just "coming up to speed," sorta. In my work I typically get thrown into deep ends all the time, and it's fun to assymilate as much information and knowledge as quickly as I can. Not so I'll be any kind of expert, but enough that I can understand what people are talking about, know what to watch for, perceive subtleties I might've missed, and so on. I won't keep up at this rate, but while I've got the downtime (I can't ride or do gardening, either, right now) I might as well indulge my brain.
What I'm really looking for now, though, are exercises in ... I don't even know, really (the joy of being a total noob)... focus, awareness, attitude, breathing, relaxing while moving... I'm being very patient with the physical part, but there must be other things I can be doing, meanwhile. (And it might be longer than 3 more weeks - that's "if everything goes well.")
Here are a couple I just remembered, that I could be doing: tenkan undo, and shikko.